Method and apparatus for cooling melt spun threads



1958 H. J. H. SCHEERS 2,847,704

ETHOD AND APPARATUS FOR COOLING MELT SPUN THREADS 7 Filed Sept 22, 1953 i'll 0000000a0000000000000000000000000000 n .00!OOOOIIOOQ00000000000000000000000 000000000900000000000000000000 00000 ATTORNEYS United States PatentGfiFic'e 2,847,704 Patented Aug. 19, 1958 METHOD AND APPARATUS FOR COOLING MELT SPUN THREADS.

Hermanus Joseph Hendrikus Scheers, Arnhem, Netherlands, assignor, by mesne assignments, to American Enka Corporation, Enka, N. C., a corporation of Delaware Application September 22, 1953, Serial No. 381,706

Claims priority, application Netherlands November 27, 1952 6 Claims. (Cl. 18-8) cooling andinitial stretching of the still fluid, extremely sensitive, spun material take place in a protective spinning cell. Cooling air is circulated through the spinning cell to bring about solidification of the threads.

In; spite of using a protective cell to surround the delicate thread and even with controlled circulation of the air longitudinally or transversally through thecellpundesiredtvariations in the cross sectional area and denier of. the threads persist.

Itis therefore an object of this invention toimprove the quality of melt spun threads as to uniformity of. denier and cross section.

It is proposed according to the present invention to bring about uniform flow of ventilatingair which is axial ofand symmetrical within a spinning cell andto accornplish the ventilation without the use of positiveair circulating means such as pumps, fans, and the like,,which were required in the prior art procedures for forced air movement.

The method of the present inventionis characterized by an automatic thermosyphon ventilation of the spinning cell which is brought about by perforating a portion of the cell Wall and using the heat of the freshly spun thread as the primary power supply to circulate the cooling air.

Other objects and advantages of. this invention will be apparent upon consideration of the following detailed description of a preferred embodiment thereof in conjunction with the annexed drawing, the single figure of which shows, in vertical section, a spinning cell constructed and arranged according to the teachings of the present invention.

The melt is extruded through a spinneret 4 from a conventional melt supply container 3. The spinneret 4 is arranged to extrude vertically downwardly such molten organic compounds as caprolactam polyamides or various other thermoplastic compounds such as polyvinyl deriva tives, polyacrylic acid derivatives, polyesters, polyethers and polyamides. The method and apparatus of the present invention is quite suitable for use with compounds such as polyvinyl esters, polyvinyl chloride, polystyrene, polyacetals, and polyethyleneterephthalates.

Upon extrusion, the molten plastic thread 8 is allowed to solidify by cooling within a cylindrical chamber 1, which co-axially surrounds the spinneret 4 and depends vertically from the melt supply container 3 which, with the spinneret, closesthe top of the chamber. A heat insulating collar 2 surrounds the upper end of the chamber 1 adjacent to the spinneret. From the bottom ofjhis collar for a vertical distance. .h thetubular chamber} is unperforated. Then for a vertical distance k it is perforated -and, belowtheperforatedarea, it is ;again unper forated. The bottom of the tubular chamber 1 is open to atmosphere and the bundle offilarnents which constitutes the thread 8 passes axially through the entire length of the chamber 1 andissues from its open mouth at the bottom.

The tubular chamber 1 is .coaxially surrounded by a large tube 9 which overlaps the perforated arca e, and extends axially at least into the unperforated area or zon elS, although the samemay also, extend axially below thearea 6 in the manner shown in the. drawing". The large tube 9 is openat both ends, and its v lower end .11 is surrounded bya protective sleeve 12, which is, a its lower end, sealed to the chamber 1 by an annular disl. i3. It is .now evidentthat air surrounding the thread 8 will beheated by. direct contact with the thread. The heating of theairin the chamber 1 will cause it to flow upwardly in the direction of the arrows. When it reaches the perforated zone 6 of the tube 1, the heated air will pass throughthe perforations and induce a flow in the annular space 14 between the tubel and the tube 9. Cooling air will enter the space 14 from the bottom through the open top 15 of the sleeve 12 as indicated by the arrows.

It can be seen that the structure. described resultsin the heat energization of the air within the chamber l. Thus, the heat lost by the thread is used to propel the coolingain. The air moving in the annular space 14 cools the spinning cell and facilitates. automatic ventilation of the cell by a kind of ejection action.

Where the deniers are low and the spinning speed is low, the length of the chamber 1 may be only from eighty to. one .hundred centimeters, When the deniers are higher and the spinning speed is higher, the chamber 1 must *be much longer in order to coolthe larger quantity of ,faster movingthread, Thus, it is contemplated that the chamber may be as long as fromtwo to four meters. The unperforated area 5 of the chamber 1 is at least ten centimeters is length for low denier threads, and, for threads of higher denier, it may be as great asthirty centimeters. If the chamber 1 is quite short, the perforations may extend forthe full length below the zone 5, but, for a long chamber, the perforated zone should be at least one hundred centimeters in length. The perforations must be symmetrically distributed around the circumference of the chamber 1, throughout the entire axial length of the perforate zone. Holes of from one to five millimeters in diameter have given satisfaction. Too large holes may bring about discrepancies in the air flow and too small ones may offer excessive resistance to flow and may be closed by condensation of by-products of the thread.

It is possible, under certain conditions, to have the perforations of the spinning chamber wall decreasing from top to bottom. This may be attained by decreasing the diameter of the holes from top to bottom with constant number of holes per unit surface, or by decreasing the number of holes per unit surface with constant diameter of holes.

It is, however, by no means necessary for the holes to be circular. The perforation may have any shape, e. g. a slit shape, provided the passage and the resistance of the individual holes are not too great, and the holes give no rise to clogging.

There are no hard and fast rules for giving the absolute measure of perforations, e. g. expressed as the ratio total hole surface to perforated surface of the spinning chamber. It should be determined for every case. This ratio depends, among other things, upon the denier of the thread to be spun, upon the speed at which the thread is to be spun and uponthe amount of heat brought into the spinning chamber by the spinning mass from the spinneret per unit time.

There is also a certain dependence on the spinning chamber diameter and on the resistance the fresh air has to overcome on entering the spinning chamber.

It has been found, though, that in most cases the perforation ratio: sum of hole surfaces to perforated surface of the spinning chamber is within the range one to twenty-five percent.

As an example of the operation of the present device, a six-filament, one hundred denier caprolactam thread was spun at a drawoif speed of eight hundred meters a minute. The chamber 1 was one hundred thirty centimeters long. The perforations were three millimeters in diameters and the perforation ratio was four percent in the area 6. In other Words, four percent of the available surface of the tube 1 in the axial length h was perforated. The diameter of the tube 1 may of course vary with the size of the thread being spun.

It will be noted that the large tube 9 and sleeve 12 protect the air issuing from the perforations against drafts and promote the regular symmetrical air loss from the tube 1.

What is claimed is:

1. A spinning cell comprising means to extrude a molten plastic thread in a path extending downwardly along a vertical axis, a first tubular chamber concentrically surrounding said path, said first chamber having an unperforated area at its upper end and a perforated area adjacent to and immediately below said unperforated area, and a second tubular chamber concentrically surrounding at least a portion of the perforated area in spaced relation to said first chamber and extending axially beyond said perforated area into overlapping relationship with said unperforated area, said second chamber being open at its upper and lower ends.

2. A spinning cell as set forth in claim 1 wherein said first tubular chamber is sealed at its upper end by said plastic extrusion means.

3. A spinning cell comprising means including a spinneret to extrude a molten plastic thread in a path extending downwardly along a vertical axis, a first tubular chamber concentrically surrounding said path, said first chamber having an unperforated area extending at least 10 cm. downwardly from the upper end thereof and a perforated area adjacent to and immediately below said unperforated area, and a second tubular chamber concentrically surrounding at least a portion of the perforated area in spaced relation to said first chamber and extending axially beyond said perforated area into overlapping relationship with said unperforated area, said second chamber being open at its upper and lower ends.

4. A spinning cell as set forth in claim 3 wherein the total area of the perforations decreases per unit length from the upper to the lower end of said first chamber.

5. A spinning cell comprising means to extrude a molten plastic thread in a path extending downwardly along a vertical axis, a first tubular chamber concentrically surrounding said path, said first chamber having an unperforated area at its upper end and a perforated area adjacent to and immediately below said unperforated area, a second tubular chamber concentrically surrounding at least a portion of the perforated area in spaced relation to said first chamber and extending axially beyond said perforated area into overlapping relationship with said unperforated area, said second chamber being open at its upper and lower ends, and a protective sleeve concentrically surrounding the lower end of said second chamber in spaced relation thereto, said sleeve being open at its upper end and closed at its lower end.

6. In the manufacture of artificial threads, the automatic thermosyphon ventilation process comprising the steps of extruding a molten thermoplastic thread vertically downwardly into contact with a first column of air, causing said first column of air to flow upwardly primarily as a result of the heating thereof upon contact with the freshly extruded thread, and maintaining limited contact between the heated first column of air and a second column of air concentrically disposed thereabout, thereby inducing upward flow only in said second column of air in a zone concentric with but disposed outwardly of said first column of air as a result of the heating thereof upon contact with the heated first column, whereby a uniform flow of ventilating air axially of the extruded thread is accomplished without the use of positive air circulating means.

References Cited in the file of this patent UNITED STATES PATENTS 1,861,912 Friedrich June 7, 1932 1,959,414 Dreyfus May 22, 1934 2,252,684 Babcock Aug. 19, 1941 FOREIGN PATENTS 565,282 Great Britain Nov. 3, 1944 

